Heater



FIG. 1 is a front elevation view of a heater, showing our new design;

FIG. 2 is a rear elevation view thereof;

FIG. 3 is a right elevation view thereof;

FIG. 4 is a left elevation view thereof;

FIG. 5 is a top plan view thereof;

FIG. 6 is a bottom plan view thereof;

FIG. 7 is a front perspective view thereof; and,

FIG. 8 is a rear perspective view thereof.

The broken lines in the FIGURES show portions of the heater which form no part of the claimed design. 

CLAIM The ornamental design for a heater, as shown and described. 